[texhax] Strange behavior of \mathop

[Michael Barr]

I was vaguely aware that \mathop sometimes lowers its argumet, but I was 
unprepared for this.  Look at the following two, nearly identical files, 
paying close attention to the vertical placement of the bold "E"s.

\documentclass[12pt]{article}
\def\E{\mathop{\bf E}}
\begin{document}
$x\E y$ $x\E y$
\end{document}

\documentclass[12pt]{article}
\def\E{\mathop{\bf E}}
\begin{document}
$xE y$ $x\E(S)y$
\end{document}

Michael